Interspecific cornus hybrid designated &#39;kn4-43&#39;

ABSTRACT

An interspecific hybrid of  Cornus kousa×C. nuttallii exhibits the vigorous nature and the floral display of large, white bracts of plants of    C. nuttallii  and the dark, glossy green foliage and disease and insect resistance of plants of  C. kousa . The hybrid thus provides a new, unique, and sperior large-braed dogwood for landscaping purposes. Plants of  C. nuttallii  become very large in nature in areas where they are indigenous but seldom thrive in other areas. Plants of this novel hybrid are expected to thrive in many regions of the world where plants of  C. kousa  perform well.

BOTANICAL DESCRIPTION

Botanic name: F₁ interspecific hybrid of Corns kousa×C. nuttallii

VARIETY DENOMINATION

KN443

BACKGROUND OF THE INVENTION

This new cultivar is the product of a long standing detailed program of interspecific hybridization and selection of dogwoods, in this instance from hybrid seedlings of Cornus kousa an ornamental Asiatic dogwood and Cornus nuttallii, a giant, large bracted dogwood that is indigenous to the Pacific Northwest of North America. Records of these hybrids were carefully retained and characteristics analyzed for their differences and outstanding value as potential commercial varieties or cultivars.

We have selected the particular seedling hereof from certain progeny grown in a cultivated area and, as a result, have in turn caused the same to be asexually reproduced by grafting (usually T-budding or chip-budding). It also can be propagated by softwood cuttings. The reproduction and actual growth and selection of the new cultivar took place in the vicinity of New Brunswick, N.J. and has been found to be distinctive as to its vegetative winter-hardiness in that area, USDA Plant Hardiness Map Zone 6a.

As will be understood from the detailed description of the invention which appears hereinafter, the new cultivar is in fact outstanding and readily identified as being such. With the foregoing in mind, the description which allows will be understood as clearly defining the new cultivar, the desirable characteristics of which are the result of such a program as has been heretofore suggested.

SUMMARY OF THE INVENTION

The variety was originated or discovered on Horticulture Farm No. 1 of New Jersey Agricultural Experiment Station, Ryders Lane at US Route 1, New Brunswick, N.J. 08901, Middlesex County. This seedling resulted from a controlled cross successfully S accomplished on May 4, 1973. The seedling which became this new variety germinated Apr. 15, 1974, was field planted Mar. 17, 1975, as Plant 22 in Row 52 of research field No. 22 and is still at this location as a thirty-year-old plant. The seed parent is Cornus kousa (Buerger ex. Miq.) Hance ‘Simpson No. 1’ (Non-patented). The pollen parent is Cornus nuttallii Aud. ‘Goldspot’ (Non-patented). Reproduction took place on Horticulture Farm No. 1, Rutgers University, New Brunswick, N.J. It has also been propagated by nurserymen in Tennessee, Oregon, and California under formal testing agreement with the NJAES, Cook College/Rutgers University. To the best of our knowledge, this new variety is the first reported F₁ interspecific hybrid involving plants of these two species.

BRIEF DESCRIPTION OF THE DRAWINGS

This new cultivar of dogwood is illustrated by the accompanying photographic drawings, depicting the plant by the best possible color representation using color photogruphy. All color references below are measured it The Royal Horticultural Society (RHS) Colour Chart. Colors are approximate as color depends on horticultural practices, such as light level and fertilization rate, among others.

FIG. 1 shows the oinal dogwood tree of the present invention after 30 growing seasons; and

FIG. 2 shows a single flower head of the tree shown in FIG. 1 taken at the time off floral display, and indicates the color and shape of the floral bracts.

BOTANICAL DESCRIPTION OF THE INVENTION Plant

-   Form: Tree. -   Growth habit: erect and uniformly wide. -   Growth: Very vigorous; densely branched and foliaged. -   Height: 8.83 m tall at 30 years. -   Spread: 7.07 m in diameter at 30 years. -   Plant vigor: This new interspecific F₁ hybrid is less vigorous than     the C. nuttalii parent as plants of C. nuttallii are the giants of     the large-bed dogwoods, reaching 24 meters in nature in the Pacific     Northwest of North America where the plants are indigenous. However,     plants of this hybrid are at least 100% more vigorous than typical     plants of C. kousa. One-year liners of this hybrid propagated in     Oregon by budding are nearly twice the size of one-year liners of C.     kousa as the hybrid liners typically are 1.2 m in height and are     very stout. -   Cold hardiness: Plants are vegetatively hardy in USDA Plant     Hardiness Map Zone 6a (−5° to −10° F.) but the floral display of the     involucral bracts is very poor as developed of the bracts is     arrested due to winter-kill of many flowers of the inflorescce.     Plants exhibit good floral display in areas of Plant Hardiness Map     Zone 7a (+5° to 0° F.). Plants are subject to “bark-split” on the     souffi and/or west sides of the tree trunk on briht, sunny days     during January in USDA Plant Hardiness Map Zone 6a. -   Resistance to insects and disease: No insect or disease problems     have been observed during the twenty-eight years the original F₁     interspecific hybrid seedling has been tested in the field. -   Trunk: Circumference of the crown of the original seedling at the     soil level, below the three upright trunks, was 1.57 m at 30 years.     -   -   Color.—a mottle of spots of 197C and 197D (Greyed-Green             Group).         -   Texture.—Sandpaper rough, bark exfoliating on lowest 3 to 4             feet. Color of under exfoliating bark: a mottle of spots             166D (Greyed-Orange Group) and spots of 174B and/or spots of             174C (Greyed Orange Group). -   Branches:     -   -   Color.—Brown Group 200B and 197B, 198D Greyed-Green Group.         -   Texture.—Smooth, with tiny rough bumps (lenticels).         -   Crotch angle.—75°.         -   Lenticels.—Length: 1.25-1.75 mm Width: 0.4-0.65 mm Color:             closest to and/or in between 197A and 197B Greyed-Green             Group Number abundant but density variable. Average (n=4)             number of lenticels per cm² is 124.5.         -   Internode length.—5-7 cms.

Foliage

-   Leaf arrangement: Opposite.

Leaf size — blade: Average length Average width Year n (in cm) n (in cm) 2001 31 11.02 31 6.16 2002 30 10.33 30 5.92 Wherein ‘n’ as used throughout this description represents the number of measurements Wherein ‘n’ as used throughout this description represents the number of measurements utilized to obtain the average measurements stated.

-   -   -   Shape.—elliptic.         -   Tip.—apiculate.         -   Base.—obtuse.         -   Margin.—entire.

-   Other features: Prominent midrib on abaxial surface, average of 5-6     secondary vein pairs; tufts of fine, whitish-tan pubescence at axils     of midrib and secondary veins on abaxial surface of leaf iterveinal     areas of blade have scattered pubescence.

-   Quantity: densely foliated.

-   Coloration: Solid.

-   Spring foliage color adaxial: 137A Green Group Abaxial: 137C Green     Group.

-   Mature foliage color — adaxial: 139A Green Group Abaxial: 137C Green     Group

-   Autumn foliage color (november): Of little ornamental value as about     70 percent of the leaves are nearly fill green: 137A Green Group;     the other leaves are 50 to 70 percent green (137A Green Group) with     the remaining surf areas mottled with colors ranging from yellow     (21B Yellow-Orage Group) to yellow and orange and red (21B     Yellow-Orange Group; close to 46A Red Group but not as bright; 178A     Greyed-Red Group) and red to burgundy (187A Greyed-Purple Group).

-   Texture:     -   -   Adaxial side.—Glossy, smooth.         -   Abaxial side.—Flat and smooth with prominent midrib.

-   Ribs and veins: prominent midrib on abaxial surface.

-   Petiole: Color: 144A Yellow-Green Group (Spring and Summer); 144C     (Autumn).

-   Stipi;es: Exstipulate.

-   Disease resistance: Not susceptible to powdery mildew or dogwood     anthracnose in central New Jersey, in Boring, Or. or in Winchester,     Tenn.

Inflorescence

-   Location where observations were made: Animal Research Farm, NJAES,     North Brunswick, N.J. -   Type of inflorescence: flower head; Dense, rounded mound. -   Average height and diameter of over-wintering flower buds is 8.7 mm     and 6.25 mm (n=10), repectively.

Peduncle: Year n Average length (cm) n Average width (cm) 1999 24 1.82 24 2.72 2001 25 1.77 19 3.24 2002 60 1.60 60 3.23 2003 33 1.48 33 3.14

-   The average peduncle length of this interspecific hybrid at the time     of floral display is much shorter than that of its parent plants as     the peduncle length for plants of C. nuttallii and C. kousa ranges     from 3 to 8 cm and 5 to 10 cm, respectively. Color: 138C Green     Group. -   Vegetative bracts bome on peduncle: Two to three pair of opposing     appressed bracts closely telescoped on the pedunecle. Shape is that     of an elongated isosceles triangle, the tips of the uppermost pair     of bracts occasionally touch the basal pair of floral bracts at the     base of the flower head. -   Size of vegetative bracts: variable, from 5 to 9 mm in length and     4-5 mm in width at base. -   Point of insertion on the peduncle is relatively far below the     flower head, i.e., near the base of the peduncle. -   Color of vegetative bracts: Closest to 145A Yellow-Green Group but     16A Greyed-Orange Group at the apex and along the margins of the     bracts. -   The vegetative bracts are similar to those of the C. nuttallii     parent in being borne well below the flower head and do not enclose     the true flowers in the overwintering floral buds. The bracts are     dissimilar to those of the C. kousa parent as the upper set of     vegetative bracts in plants of C. kousa completely enclose the true     flowers in the overwintering flower buds. -   Floral bracts:     -   -   Number.—typically four (in two pairs); infrequently 5 or 6.

Size.—in cm, of upper floral bracts, as shown below: Average Average width Average Involucral Year n length (cm) (cm) Spread (cm) n 1999 50 5.01 3.96 10.30 25 2001 50 5.02 4.22 10.34 25 2002 60 5.30 4.78 10.90 30

-   Bract size will vary from year to year but the upper bracts will be     longer and narrower than the lower bracts each year. The bract size     of this new interspecific dogwood is within the size range typical     for plants of C. kousa but is considerably smaller than the     involucral spread of the C. nuttallii parent, C.n. ‘Goldspot’ which     typically involves six floral bracts measuring 6 to 7.5 cm in     length. -   Color of floral bracts:     -   -   Adaxial surface.—Closest to 155A White Group but slightly             more yellow.         -   Abaxial surface.—Closest to 155B White Group but slightly             more yellow. -   Shape of floral bracts: Broadly obovate.     -   -   Apex of floral bracts.—Abruptly acute.         -   Base of floral bracts.—cuneate. -   Flower Description:     -   -   Flowering habit.—Very floriferous. Single flowers arranged             in compact, dense heads subtended by the large floral             bracts. No observed fragrance. Flowers not persistent Floral             display of the bracts lasts about two to three weeks,             depending on weather conditions.         -   Flowering habit.—Anthesis of the tiny, relatively             inconspicuous true flowers generally commences two to four             days following the onset of the ornamental display of the             large floral bracts which in New Brunswick N.J. starts just             as the floral display of plants of C. florida ceases, or             about May 14^(th) in most years. -   Number of true flowers per flower read:     -   -   1999 75.00 (n=24).         -   2001 77.24 (n=25).         -   2002 77.30 (n=30).         -   2003 78.70 (n=10). -   The number of true flowers per flower head of our interspecific     hybrid is intermediate to that of the parent plants as the     pistillate parent (C. kousa) has about 50 flowers per flower head     and the staminate parent (C. nuttallii) typically has an average of     100 flowers per flower head.

Reproductive Organs

-   Stamens:     -   -   Number.—4.         -   Color.—pale grayish-white.         -   Filament.—Size: about 1.5 mm long and 0.25 mm wide Anthers:             Size: about 1 mm long and 0.25 mm wide Pollen: very sparse,             white with hint of yellow. -   Pistil:     -   -   Number.—1.         -   Style.—about 1.5 to 1.7 mm (including stigma 0.25 mm) long.         -   Stigma.—approximately 0.4 mm in width.         -   Color.—pale greenish-white.

Fruit

-   Flower head with fruit: Round mound with flattened base. Exterior is     rough as the single it are tightly compressed but separate and the     style and sepals protrude at the apex of each fruit. Most fruit are     pa ocarpic (without seed) as the plants are highly cross-sterile, as     well as self-incompatible, and very few seeds develop. The pericarp     of the fruit is smooth and at maturity ranges from 34 Orange-Red     Group to 42A Red Group and 44A Red Group, the fruit bearing a viable     seed being the darkest in color. A single fiuit is about 1.0 cm long     and 0.7 cm in width, ellipsoidal in shape and rather smooth if a     well developed, viable seed is present, but the parthenocarpic fruit     are smaller (shrunken) and rather angular (often 3 sided and     somewhat flattened) in shape. -   Seed color: Variable from 165E to 165C to 165D Greyed-Orange Group. -   Seed:     -   -   Size.—Approximately 8 mm long and 4-5 mm wide. 

1. A new and distinct cultivar of dogwood tree, substantially as herein shown and described, comprising an interspecific hybrid of Cornus kousa×C. nuttalli. 